This invention relates to fluid sealing connections between rigid and flexible tubular fluid conduits, and more particularly to automotive hose couplings such as those used for connecting conduits in automotive power steering systems, and for coolant conduits for transmission and engine oil cooling systems, and the like.
Crimp-type collar couplings used for sealingly telescopically coupling together rigid and flexible pressurized fluid conduits used in automotive power steering systems, and in transmission and engine cooler systems and the like, consist of a variety of designs. The sealing surface of the rigid tube at its nipple end, i.e., the end that is inserted into the open end of the flexible hose of the connected conduits so as to telescopically overlap therewith, may have a shank that is smooth or, alternatively a shank that has raised ribs, rolled ribs, or one of many other external. groove configurations. These different groove configurations are employed to enhance the sealing against fluid leakage between the flexible hose (usually made of a suitable elastomeric material), and the metal or other material used to construct the rigid tube. During the collar crimping procedure used in making the coupling, a generally cylindrical malleable metal shell is employed as a crimping collar and encircles the outside circumference of the hose. This collar is permanently circumferentially and radially-shrunk deformed to thereby apply mechanical radial compression pressure to the hose and thus builds up a permanent restraining stress for frictionally clamping the hose onto the tube nipple. This shrink force is also intended to squeeze the hose inner surface or hose innermost layer (in the case of a multilayer laminated hose) into any and all grooves or valleys of whatever rib design is provided on the nipple shank sealing surface. This adds a mechanical interlock structure reinforcing the frictional clamping to thereby assure that the assembly will remain intact against tensile forces tending to pull apart the flexible hose and rigid tube at their coupling.
One feature that prior coupling designs hitherto appear to have in common is that when a plurality of machined, cast, molded or rolled ribs or grooves are provided in the nipple shank exterior surface configuration, all sharp edges (where the radial sidewalls of each groove intersect the cylindrical nipple shank outer surface) are made xe2x80x9cnon-aggressive.xe2x80x9d This is done either by initial design for eliminating or modifying them by subsequently forming them into a generous radius, chamfer or bevel edge. These non-aggressive edges assure that the tubular flexible hose of the coupled conduits is not cut during the aforementioned collar crimping operation employed to render the coupling permanent and sealed tight.
Thus conventional thinking has been that if the tube were cut during crimping by the presence of such a sharp edge, premature failure of the coupling assembly would result. On the other hand, sharp edges hitherto have been used on the barbs of rigid tubular nipples that are used in power steering or oil cooler hose. Nevertheless where grooves or ribs, instead of barbs, have been used on a nipple shank to enhance a sealing surface function the sharp edges that might otherwise have been formed, such as by leaving square cut groove corners as initially formed by lathe-turned cuts, have been purposely removed or avoided for the aforementioned reasons.
Accordingly, an object of the present invention is to provide an improved automotive hose coupling employing one or more specially contoured external grooves to enhance the sealing between the telescopic junction of the nipple shank of a rigid tubular conduit and a flexible hose in conjunction with a crimping collar that is permanently shrunk-deformed to apply radial compression pressure to the hose, and which coupling is improved from the standpoint of maximizing its sealing pressure capability while not causing the flexible hose to be cut by the crimping forces produced between the inner surface of the hose and the outer surface of the grooved tube shank of the coupling.
Another object is to provide an improved method of making an improved coupling of the foregoing character that is economical, reliable and that reduces the amount of compressive force needed for crimping the collar on the hose to effect a good seal, thereby reducing the internal stresses in the hose and minimizing the chance of damage occurring because of over-crimping in constructing the coupling.
In general, and by way of summary description and not by way of limitation, the invention achieves one or more of the foregoing, as well as other objects, by providing a pressure fluid conduit coupling, and method of making same, wherein an improved nipple tube fitting conduit is made of specially grooved rigid material for use with a conventional elastomeric hose conduit having an open end that telescopically receives an open end of a shank of the nipple fitting, and is then permanently secured together by a conventional crimp-collar sleeved over and shrunk-deformed onto the hose open end. An external circumferential surface of the tubular shank of the fitting is provided with one or more circumferentially continuous sharp edge external grooves that are defined by the ribs formed between the grooves. At least two adjacent grooves of a plurality of such grooves are spaced axially from one another by a predetermined distance W2. Each of these two grooves have a predetermined axial width dimension W1 defined by generally radially extending axially spaced sidewalls facing one another. The bottom wall of each groove extends axially between the associated groove sidewalls and is formed at a radial depth represented by the predetermined dimension H, as measured from the external maximum outside diameter of the nipple shank ribs formed between such grooves. The external circumference of the fitting shank ribs between such grooves has a cylindrical contour of constant diameter. The junction of each of the groove sidewalls with the respectively adjacent shank rib surface defines a circumferentially continuous sharp edge formed generally as a 90xc2x0 junction of these walls, plus or minus a few degrees.
Preferably for couplings designed for connecting conduits ranging in shank outside diameter from about 0.25 inches to about 0.75 inches, the groove depth dimension H is in the order of 0.008 inches, the groove width dimension W1 is in the order of about 0.030 to about 0.035 inches, and the groove spacing dimension W2 is in the order of about 0.060 to about 0.070 inches. However, improved results also can be obtained within a range of such dimensional parameters, e.g., the groove depth dimension H may range between about 0.004 inches to about 0.015 inches, the groove width dimension W1 may range between about 0.025 inches to about 0.040 inches, and the groove spacing dimension W2 may range from about 0.055 inches to about 0.070 inches. Preferably the number of the grooves in the plurality of grooves ranges from about four to eight, and the groove dimensions W1, W2 and H apply to all of such grooves and are uniform and constant from groove-to-groove.
Preferably the crimp-collar is crimped to permanently deform the same with a magnitude to create, in the hose inner surface area impinged by at least one of the sharp edge comers of the grooves, an internal stress in the hose up to about 700 psi. Also, the crimp-collar is preferably shrunk by an amount sufficient only to radially compress the thickness dimension of the wall of the flexible hose conduit, where the hose wall is encircled by the collar, to about 80 percent of its free state thickness.